Martensitic transformation and shape memory effect under magnetic field for Ni2MnGa sputtered films containing iron

The effect of iron addition on the martensitic transformation (MT) and shape memory effect (SME) of the Ni2MnGa sputtered films was investigated. It was found that the constraint-aged films with more than 8.5 mol% Fe have two phases. MT temperatures monotonously decreased with increasing amount of iron addition, while the Curie temperature increased. The reversible two-way SME by the thermal change was confirmed for all constraint-aged films containing iron through the MT and its reversion. Furthermore, the SME by magnetic field was observed around the MT temperature on cooling for the films containing iron in which MT occurred within the ferromagnetic region. The strain change in a low magnetic field of 1 T became large for the films containing iron. The behavior is as expected from the MT induced by the low magnetic field.